1. Field of the Invention
The present invention relates to an ink jet recording head, an ink jet recording apparatus, and a method for manufacturing the ink jet recording head and, more particularly, to the structure and construction of a connecting section between a recording element substrate (liquid discharging substrate) on which a recording element (energy generating means) is provided and a wiring substrate for supplying power thereto.
2. Related Background Art
An ink jet recording apparatus, a so-called non-impact type recording apparatus, refers to an apparatus for recording information by discharging recording liquid (ink) onto a subject medium. This type of ink jet recording apparatus has excellent features such as high speed recording, compatibility with a variety of recording media as the subject medium in recording, and little noise production during recording. These features of the ink jet recording apparatus render it suitable for wide use as a printer or an apparatus equipped with a recording mechanism such as a word processor, a facsimile, a copy machine, etc.
Typically, this type of ink jet recording apparatus comprises an ink jet recording head including a plurality of ink jet recording nozzles, each having a discharge port for discharging liquid drops and a recording element for generating energy to discharge the liquid drops; and a liquid supply system for supplying liquid to the ink jet recording head. There are two types of ink jet recording head: one type (edge shooter) discharges recording liquid in parallel with a substrate on which the recording elements are arrayed, and the other type (side shooter) discharges recording liquid perpendicularly to a substrate on which recording elements are arrayed.
The ink jet recording head typically employs a method for using an electric thermal converting element as the recording element. By this method, thermal energy is given to liquid to utilize the pressure of bubbles produced when the liquid subsequently changes in phase to foam (boils), in order to discharge drops of the recording liquid. An ink jet recording apparatus employing such a recording method specifically supplies as a recording signal an electric pulse to an electric thermal converting element, which in turn generates thermal energy to bring about film boiling of the liquid in order to generate a pressure, which causes minute drops of the liquid to be discharged from a minute ejection outlet, thereby recording information on a subject medium.
FIG. 14 shows a recording element substrate 101 constituting an important section of a side shooter type ink jet recording head that has been used conventionally. The figure is a partially exploded perspective view.
The recording element substrate 101 comprises a substrate 102, and a member 123 including electric wiring and a liquid chamber filled with ink, which are formed on the substrate 102 by film forming technologies. The substrate 102 is made of silicon formed to a thickness of, for example, 0.5 to 1.0 mm. In the substrate 102 is formed a plurality of ink supply outlets 103 each consisting of an elongated groove shape through-outlet for receiving liquid into the liquid chamber from the outside. On either side of each of the ink supply outlets 103 on the substrate 102 a row of electric thermal converting elements 104 is arrayed. Each row is staggered with respect to its adjacent rows.
The liquid chamber is formed so that it may communicate with each of the ink supply outlets 103 and also so that it may enclose the electric thermal converting elements 104 formed on both the sides of each ink supply outlet 103. In the liquid chamber there is formed an ink flow path wall 107 constituting ink flow paths running through positions above the electric thermal converting elements 104, respectively, and there are also formed ejection outlets 108 above the electric thermal converting elements 104, respectively.
Furthermore, on the substrate 102 is formed an electric wiring line (not shown) made of aluminum (Al) for supplying power to each of the electric thermal converting elements 104, which wiring line is connected to an electrode section 105 connected to an external power supply. The electrode section 105 is provided roughly at each of two longitudinal ends on the substrate 102, and it has a plurality of arrayed connecting members 106 (xe2x80x9cbumpsxe2x80x9d) made of gold (Au).
However, an ink jet recording head using the above-described recording element substrate 101 has the following problems.
In order to implement recent photo-grade improvements in the number of colors and the picture quality of a recorded image, the ink jet recording head has been designed to have a larger number of nozzles and a smaller pitch between the nozzles. With this, therefore, the electric thermal converting elements formed on the recording element substrate have also been devised to be more numerous and less spaced from each other. Besides, along with improving functions of the electric thermal converting elements, the bumps 106 of the electrode section 105 have also been devised to be more numerous and less spaced from each other. This has brought about a larger risk of poor connection such as open-circuiting or short-circuiting occurring between the bumps 106 and the respective connecting terminals of electric wiring lines connected to an external power supply when they are connected with each other, thus leading to significant decrease in the packaging yield and the packaging reliability.
Furthermore, with the improvements in the number of colors and the picture quality, the number of nozzles, and hence the number of electric thermal converting elements, on the recording element substrate has been increased, thus increasing the power supplied to the electric thermal converter. This has brought about the need to suppress the connection resistance between the recording element substrate and the electric wiring substrate.
Furthermore, the higher density of the electric thermal converters and hence of the electric wiring lines has been a factor in the increased cost of ink jet recording heads. To solve these problems, it is desired to improve the packaging yield and reliability and reduce the connection resistance without increasing the costs significantly.
The present invention is devised taking into account the above-mentioned problems of the conventional technologies. It is, therefore, an object of the present invention to provide an ink jet recording head having a recording element substrate on which power supply paths are formed densely, and electric wiring for connecting the recording element substrate to an external device, so as to be able to prevent poor connections, such as open-circuiting or short-circuiting, from occurring between the recording element substrate and connecting terminals of the electric wiring, in order to thereby improve the packaging yield and reliability and also to reduce the connection resistance when the recording element substrate and the electric wiring are connected with each other. It is another object of the present invention to provide such an ink jet recording head without increasing the manufacturing costs thereof significantly.
To this end, an ink jet recording head according to the present invention comprises:
a liquid discharging substrate provided with both (1) a plurality of energy generating elements for generating energy utilized to discharge liquid from each of a plurality of ejection outlets in response to an electric signal and (2) a plurality of connecting members electrically connected to said plurality of energy generating elements, respectively; and
an electric wiring substrate having a plurality of connecting terminals connected to said plurality of connecting members, respectively, for transmitting an electric signal supplied from the outside to said plurality of energy generating elements, respectively, wherein:
each of said plurality of connecting members protrudes from said liquid discharging substrate by a predetermined protrusion amount;
said liquid discharging substrate has, between said plurality of connecting members, an insulating member comprised of at least one member protruding in the same direction as said plurality of connecting members; and
the protrusion amount of said insulating members is larger than the protrusion amount of each of said plurality of connecting members.
By this configuration, it is possible to fit each of said plurality of connecting terminals between a respective pair of adjacent insulating members so that said each of said plurality of connecting terminals may come in good contact with a respective one of said plurality of connecting members when said liquid discharging substrate and said electric wiring substrate are fixed to each other, with a sufficient contact area provided between each of said plurality of connecting terminals and the respective one of said plurality of connecting members, without short-circuiting or open-circuiting.
Preferably, the insulating member placed between each two adjacent ones of said plurality of connecting members is formed of the same material as the liquid chamber filled with liquid and in the same process as that for forming the liquid chamber, in a step for forming the member constituting the liquid chamber on the liquid discharging substrate, preferably, by photolithography. It is thus possible to form the insulating members with little increase in the manufacturing costs. Moreover, if the liquid chamber is comprised of an orifice member and a partition member, preferably the insulating member placed between each two adjacent connecting members is formed of the same material as the partition member and in the same process as that for forming the partition member, preferably, by photolithography.
In the ink jet recording head of the present invention, preferably, any of the following methods is employed to suitably electrically interconnect the connecting members and the connecting terminals, respectively, with a suppressed contact resistance therebetween.
One method comprises the steps of:
filling a gap between a liquid discharging substrate and an electric wiring substrate with a thermo-hardening adhesive agent around connecting sections, respectively, of each connecting member and its corresponding connecting terminal in a state where said each connecting member and said each connecting terminal are arranged on said liquid discharging substrate and said electric wiring substrate, respectively, in such a manner as to be in contact with each other; and
heating and thereby hardening said thermo-hardening adhesive agent by applying a pressure across said liquid discharging substrate and said electric wiring substrate in such a direction as to press said connecting members and said connecting terminal to each other, respectively.
In this case, preferably the thermo-hardening adhesive agent is an anisotropic conductive one containing conductive particulates, because this type of thermo-hardening adhesive agent is suitable for high-density packaging.
Another method involves gang bonding by means of heating the connecting member and the connecting terminals under pressure. A further method involves single-point bonding by means of a supersonic load on each connecting member and each connecting terminal.
An ink jet recording apparatus according to the present invention comprises the above-mentioned ink jet recording head mounted thereon. This ink jet recording apparatus can suitably supply power with a low resistance to energy generating means provided in the ink jet recording element and so can suitably drive each of the energy generating means to thereby record an image with a high picture quality.
An ink jet recording head manufacturing method according to the present invention comprises the steps of:
forming on a liquid discharging substrate a plurality of energy generating elements for generating energy utilized to discharge liquid from discharge ports in response to an electric signal;
forming on said liquid discharging substrate a plurality of connecting members which are connected to said energy generating elements, respectively, and which protrude from a surface of said liquid discharging substrate by a predetermined protrusion amount;
forming, between every two adjacent ones of said plurality of connecting members on said liquid discharging substrate, an insulating member comprised of at least one member protruding more than said predetermined protrusion amount, in the same direction as that in which said plurality of connecting members protrude;
fitting each of a plurality of connecting terminals, which is provided on an electric wiring substrate and connected with a respective one of said plurality of connecting members, between two adjacent insulating members so that said connecting terminals and said connecting member may come in contact with each other, respectively, in order to transmit an electric signal supplied from the outside to said energy generating elements, respectively; and
fixing said liquid discharging substrate and said electric wiring substrate to each other in such a position that respective connecting members and connecting terminals come in contact with each other.